1. Field of the Invention
The present invention relates to a rear derailleur bracket for connecting a rear derailleur to a bicycle frame, utilizing a coupling portion formed on a derailleur mounting extension of a rear fork end of the bicycle frame.
2. Description of the Related Art
Conventionally, where a bicycle has a frame including a derailleur mounting extension of a rear fork end, a rear derailleur bracket is directly connected to a coupling portion, such as a cutout portion, formed on the derailleur mounting extension. A rear derailleur is attached to the bicycle frame through the rear derailleur bracket.
It was around 1952 when the first example of bicycle frame structure appeared in which a rear derailleur was attached directly to the derailleur mounting extension of the rear fork end. From that time to this day, where the bicycle frame includes the derailleur mounting extension, the derailleur, regardless of its specifications, has been regarded as being designed for direct connection to the derailleur mounting extension. This direct connection of the rear derailleur has continued as an established practice.
Certain types of rear derailleurs directly connected to the rear fork end heretofore are not well suited to the bicycle frame configuration. This fails to attain an optimal state of attachment, resulting in a poor shifting performance. When the rear derailleur is attached, its guide wheel is located relatively far apart in a forward direction of the bicycle from rear gears. To change the chain from one gear to another, the guide wheel moves to a lateral position relatively remote from the gears. Such a shifting operation of the rear derailleur does not achieve high efficiency in disengaging and engaging the chain. Thus, the rear derailleur has a reduced shifting operability.